1. Field of the Invention
The present invention relates to articles which contain information which is in safely concealed but readily accessible form. More specifically, the present invention relates to multilayered card products which contain information in invisible form, such as in the form of letters or numbers (indicia), which can be quickly developed into observable form, but only by causing an irreversible chemical change in the structure of the multilayered card.
2. Description of the Prior Art
The problem of maintaining recorded information secret is well known to the prior art and has resulted in the development of many schemes for protecting such information from discovery by unauthorized persons. Thus, for example, in the commercial world as well as in the conduct of military and diplomatic affairs, complicated codes have been developed whereby written information can be transmitted from one place to another. Other schemes have included the transmission of recorded information in a form ordinarily invisible to the naked eye, but which can be readily made visible or audible by special sensing mechanisms or chemicals.
However, in general these transmission methods do not have means for revealing whether or not the information being transmitted has been tampered with or exposed in it passage from source to destination. Moreover, many of the prior art transmission systems require elaborate technical procedures to render the information readable.
Commonplace situations wherein secret information transmission is utilized and wherein discovery of any tampering or unauthorized premature detection thereof is essential include banking transactions wherein a customer is issued a card containing a personalized, secret bank credit or debit number which allows the customer to "unlock" the bank's automatic teller computor located outside the bank's premises; ticket sales situations, such as game or lottery ticket sales, e.g., of the "instant winner" type, wherein the purchaser reads the secret information imprinted on or within the ticket to determine if he or she is an immediate winner; etc. Obviously, a critical aspect of these types of situations is an ability to readily determine whether or not the information contained on or within the issued article has been prematurely detected by an unauthorized person.
Turning now to the prior patents in this field, in Shrewsbury et al., U.S. Pat. No. 3,001,886 of Sept. 26, 1961, an article is disclosed for incorporating and transmitting concealed information which includes a foundation film (which may be transparent), an opaque metal coating thereover, a transparent layer upon which the intended indicia is visibly printed, a transparent overlayer, an opaque metal coating located over the overlayer, and finally a top, random pattern layer. In order to "read" the indicia, the random pattern layer and opaque metal coating thereunder must be removed by erasing, e.g., with an ordinary pencil eraser, in order to expose the underlying indicia. However, these articles are not completely safe from unauthorized premature detection: as inferred at the bottom of column 2 of this patent it is possible to closely duplicate the opaque metal coating with the proper equipment; and as noted at the top of column 3, if the original pattern of the top random pattern should be somehow closely reproduced (i.e., after unauthorized detection of the underlying indicia by removal thereof), the only possible way to discover this tampering is by comparing photographs of the new patterned coating with photographs of the original. Thus, it can be seen that the Shrewsbury et al article is not only complicated in manufacture, requiring the application of multiple metal layers as well as a top patterned layer to a foundation film, but the product is still susceptible to tampering without detection. In any event, detection of tampering may require photographs of the original top patterned layer which generally will not be available.
The prior art in fact lacks an easily manufactured card product which can have its concealed information readily exposed, but wherein any tampering therewith in order to discover the information contained therein is immediately detectable.
In the field of carbonless copy papers it is known to coat the backside of a suitable sheet material, such as a paper web, with a continuous layer of dye precursor-containing, pressure-rupturable microcapsules to form a CB (coated-back) sheet, and to place this sheet into appropriate contact with a continuously sensitized surface of a second sheet, called a CF (coated-front) sheet, and thereby form a carbonless multilayer copy system. The pressure produced by a suitable instrument on the front or exposed side of the CB sheet causes rupturing of the adjacent microcapsules on the backside of the CB and the ultimate formation of a colored image on the sensitized (or color-developer) coating on the CF which corresponds to the shape of image produced on the CB by the employed instrument. Such systems are disclosed, for example, in Green, U.S. Pat. No. 2,712,507; Macaulay, U.S. Pat. No. 3,016,308; and others.
In addition to the foregoing, it is known to apply the layer containing pressure-rupturable dye precursor-containing microcapsules to the backside of the CB sheet in predetermined zones, and to additionally correlate these zones with correspondingly sensitized zones on the CF sheet. Such a technique is taught by Vassiliades in U.S. Pat. No. 3,914,511 of Oct. 4, 1975. Thus, according to this patent, instead of continuously coating the backside of the CB sheet with a layer containing microcapsules and the frontside of the CF sheet with a layer containing a sensitized agent, only specific areas of the CB and CF are so coated. In this way the transfer of data from top sheet to bottom sheet is prevented in the uncoated areas (due to the absence of either or both of the reactant components necessary for such transfer). This system provides for an efficient and less expensive way for production of copy materials when preparing carbonless-type billing invoices wherein certain data is to be included in the top (CB) sheet but excluded on the bottom (CF) sheet. This system, however, does not have as its object, nor indeed can it be employed, for producing multilayered sheet products containing latent (invisible) information which can be instantaneously developed by the user or holder thereof.
According to Cormack et al., U.S. Pat. No. 2,777,780 of Jan. 15, 1957, it is known to prepare billing invoices by applying desensitizing compounds to selected areas of a bottom (CF) sheet, these sheets having been previously coated in a continuous fashion with a layer containing a sensitized electron-accepting color-developer compound, to prevent information transfer from CB to the CF sheet. The desensitizing compounds, which may include cationic quaternary salts, aliphatic or aryl amine acetates, amines and diamines of high molecular weight and substituted oxazolines, inactivate the electron-accepting compounds (which may include attapulgite, kaolin, bentonite, etc.). According to this patent, the desensitizing compounds are applied in solution form to the sensitized color-developer coating on the CF sheet by standard printing techniques. However, as with Vassiliades, this Cormack et al. product has only large block zones of the CF sheet desensitized such that information manually recorded on the top (CB) sheet by stylus impression will not instantaneously reproduced on the bottom (CF) sheet. Thus, as with Vassiliades, this system does not have as its object, nor is it even suggested therein to produce multilayered sheet products containing latent concealed information which can be instantaneously developed by the user or holder thereof.
In the Skinner patents, i.e., U.S. Pat. Nos. 3,363,336; 3,363,337 and 3,363,338, teaching devices are disclosed which comprise single work sheets which have their surfaces appropriately treated such that differing visual effects can be achieved when writing is attempted thereon. In one embodiment invisible chemicals are applied to the surfaces of the work sheets in patterns which represent the shape of letters or numbers, and when the student writes thereon (in an attempt to himself reproduce the appropriate letter or number) with pen containing a suitable coreactant chemical, the mark so made appears as a colored trace. In this way the student can immediately see the trace of the mark he has made and be reassured that he is tracing the letter or number in the correct fashion. The area adjacent to the so-treated (or untreated as the case may be) area is such that if the student's writing instrument strays into this area no mark or trace will appear. Thus the student will immediately realize that he has made a mistake in tracing the corresponding letter or numeral. However, these Skinner patents do not relate to multilayered sheet systems and are limited to either instantaneously displaying (nor not displaying as the case may be) a mark as it is written. No provision is made for the production of a multilayered sheet system which can contain latent, invisible information which can be instantaneously displayed by rubbing of the top or bottom sheets.
A variation of the Skinner concept is taught in Manske, U.S. Pat. No. 3,682,673, wherein a work sheet has coated thereon (in the shape of the desired letters or numbers) a DTO-type reactant which, when contacted with a suitable reactant-containing solution from a chemical pen, will produce a visible mark. The DTO-type reactant is applied to the work sheet by placing thereover a top sheet which has coated thereon a layer of microencapsulated DTO derivative, and by imprinting on the exposed surface of the top sheet to rupture the corresponding microcapsules thereunder, such that the DTO-type reactant is released and migrates to the work sheet. In this way, an invisible entry is formed on the work sheet. However, in order for this hidden entry to be developed, it must be contacted with a suitable coreactant chemical.
None of the foregoing patents, however, and no other patents known at the present time, teach or suggest the production of latent image-containing carbonless CB-CF multilayered copy systems wherein the image is contained internal to the multilayered sheets and is instantaneously developable by rubbing the exposed surface of either the CB or CF sheet. Thus, even though Shrewsbury et al (U.S. Pat. No. 3,001,886 which is referred to above), discloses the possibility of utilizing a substrate which includes globules or capsules which contain reactive substances that when released, react with other substances in the production of visible characters or symbols, no enabling disclosure is provided which specifically indicates how the substrate is constructed, how it operates, or how it can be produced.
Accordingly, it is a basic object of the present invention to produce articles which contain information which is in safely concealed but readily accessible form.
It is a further object of the present invention to produce multilayered articles in the form of cards or tickets which contain invisible information, for example, in the shape of letters or numbers (indicia), which can be revealed quickly, but only by causing an irreverible chemical change in the card product.
It is a further object of the present invention to produce the foregoing products which do not require the use of optical diffusion patterns or single or multiple obscuring metal covering layers.
It is a further object of the present invention to produce multilayered articles in the form of cards or tickets which can contain invisible information, which can be passed from one person to another or sold in suitable vending machines, and which can be formed from sufficiently strong materials that their shape and integrity will remain intact during their useful life.
It is a further object of the present invention to form the above-mentioned cards or tickets using materials well known in the field of carbonless copy papers.